Anti-mass-segregated open clusters in MW

Compared to the normal population, these systems are systematically more extended (+20% in the half-mass radius), dynamically younger (~39% in dynamical age) and have longer relaxation timescales (+25%). The mass excess of anti-segregated clusters relative to normal clusters increases monotonically with dynamical age, reaching +109% at tau=5-10. Direct N-body simulations confirm that anti-segregated configurations remain stable over multiple relaxation timescales, while mass-segregated and random clusters develop strong positive segregation.

Anti-mass segregation is a dynamically stable structural state that likely reflects primordial cluster conditions. The prevalence of this configuration provides indirect constraints on the central mass content of open clusters, as massive central black holes would rapidly disrupt the anti-segregated state.